In semiconductor packaging, mold compounds are normally used to encapsulate flip-chip dies and or wire-bonding dies to protect the dies against damage from the outside environment. However, direct contact of the mold compounds and active die surfaces may adversely impact the electrical performance of the dies, especially for high frequency devices. Accordingly, it is desirable to package the dies in a configuration that is more appropriate for high frequency performance.
With developed semiconductor fabrication technology and popularity of portable communication electronic devices, such as cellular phones, tablet computers, and so forth, high levels of integration of semiconductor packages are highly desired. Package on package (POP), which stacks two or more semiconductor packages vertically, is a semiconductor packaging technology that allows higher electronics density in final products. POP offers benefits to small printed-circuit-board areas, where short trace lengths between different semiconductor packages helps enhance device performance. However, for applications that have space constraints in the z-direction (thickness), POP may not provide an optimal package solution.
Accordingly, there remains a need for improved package designs to increase the integration level of semiconductor packages and enhance the high frequency performance of the semiconductor packages without significantly increasing the package size.